npm package + IE 10 incompatibility fix (window is a const variable).

The NPM three package (http://npmjs.org/package/three) was not loading properly on Internet Explorer 10 because the variable "window" is now const and can not be modified.  Thus I have changed the header to not redefine window but rather use the made up variable THREE_window during the intialization sequence.

This works on Firefox, Chome and Internet Explorer 10.  I have not tested on other versions of Internet Explorer.

The tag for this commit incorrect says ie11, when it is really ei10.